Ecological Indicators of Forest Degradation after Forest Fire and Clear-cutting in the Siberian Larch (Larix sibirica) Stand of Mongolia

609

F

OREST

S

OCIETY

Ecological Indicators of Forest Degradation after Forest Fire and Clear-cutting in the Siberian Larch (Larix sibirica)

Stand of Mongolia

Yeong Dae Park

^1*

, Don Koo Lee

²

, John A. Stanturf

³

, Su Young Woo

⁴

and Damdinjav Zoyo

⁵

1Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea

2Department of Forest Sciences, Seoul National University, Seoul 151-921, Korea

3SRS-4104, USDA Forest Service, 320 Green Street, Athens, GA 30602, U.S.A.

4Department of Environmental Horticulture, University of Seoul, Seoul 130-143, Korea

5Institute of Botany, Mongolian Academy of Sciences, Ulaanbaatar 51, Mongolia

Abstract :

This study was conducted to investigate ecological indicators of forest degradation after forest fire and clear-cutting in the Siberian larch (

Larix sibirica

Ledeb.) stand of Mongolia. The species abundance and biodiversity indices were higher in burned and clear-cut stands than those of reference stand, but boreal understory species, such as

Vaccinium vitis-idaea

,

Pyrola incarnata

,

Linnea borealis

and

Maianthemum bifolium

, completely disappeared and was replaced by sedge species, such as

Carex duriuscula, C. lanceolata, C. pediformis, Poa attenuata

and

P. pratensis

. During the research period, temperature increased by an average of 1.6°C in burned stand and 1.7°C in clear-cut stand compared to reference stand, but RH sharply decreased up to 15.7% in clear-cut stand. This result indicates that

Larix sibirica

stand became warmer and drier after forest fire and clear-cutting, and contributed to the abundance of sedge and grass species in the understory. Moreover, intense occupation of tall sedge grass after forest fire and clear-cutting had a vital role as obstacle on natural regeneration of

Larix sibirica

. The similarity of species composition between reference and burned stands was higher (73.6%) than between reference and clear-cut stands (63.8%). Soil moisture significantly decreased after forest fire and clear-cutting, and the extent of decrease was more severe in the clear-cut stand. The chemical properties at soil organic layer were significantly affected by forest fire and clear-cutting but not the mineral horizons. Inorganic nitrogen of the forest floor significantly decreased in the clear-cut stand (1.1±0.4 mg·kg

⁻¹

) than that of the burned (4.5±2.3 mg·kg

⁻¹

) and reference stands (5.0±2.3 mg·kg

⁻¹

). Available P of the forest floor significantly increased after fire, whereas it decreased after clear-cutting. These results indicate that existence of boreal understory vegetation, and changes in soil moisture and available P are distinct attributes applicable as ecological indicators for identifying forest degradation in Mongolia.

Key words :clear-cutting, ecological indicators, forest fire, forest degradation, Siberian larch, soil prop- erties, understory vegetation

Introduction

Ecological restoration is an activity that initiates and/

or accelerates the recovery of an ecosystem that has been degraded, damaged, or destroyed (Society of Eco- logical Restoration International: SERI, 2004). The pri- mary goal of ecological restoration is to re-establish self- sustaining ecosystem (Clewell and Aronson, 2006), which is a similar concept for sustainable forest man- agement. Meeting this goal requires analysis of ecolog-

ical factors that determine limits to the ecological composition, structure, and function of an ecosystem (Wyant

et al

., 1995).

Ecological indicators are analytical and interpretive tools of ecological dynamics and can be applied to mon- itor forest degradation after disturbance and restoration management in the future (Venturelli and Galli, 2006).

To be effective indicators they should be adequately common and understood, and sensitive to underlying changes in the biophysical environment (Angelstam, 1998). Various studies have shown that understory veg- etation and forest soil properties are used as effective indicators in identifying changes in forest ecosystem

*Corresponding author E-mail: [email protected]

(Ohlson

^{et al}

., 1997; McLachlan and Bazely, 2001;

Krzic

^{et al}

., 2003). A review of basic concepts of soil and vegetation development indicates that they are mutu- ally associated with each other, both being the product of the same environmental variables.

Forests in Mongolia have been severely degraded by forest fire and clear-cutting (Tsogtbaatar, 2004). During the last decade, Mongolia lost approximately four mil- lion ha of forests, averaging to 40,000 ha annually but between 1990 and 2000, the rate of deforestation increased up to 60,000 ha per year. As a result of this ongoing loss and degradation, 1.6 million ha of forest area have been completely lost between 1974 and 2000 due to forest fire, improper cutting and clear-cutting, overgrazing, mining activities and among others (United Nations Environ- ment Programme: UNEP, 2002).

Most forests in Mongolia are composed of

Larix sibir- ica

covering about 59% of the closed forest area (Min- istry of Nature and Environment of Mongolia, 2002).

The pattern of stand development after forest fire and clear-cutting at the

Larix sibirica

stands of Mongolia mainly progressed into four stages: 1) secondary

^L.

sibrica

stand, 2) replaced hardwood stand mainly com- posed of birch and willow species, 3) bush stand, and 4) grassland (steppe), which strongly depends on the inten- sity of disturbance and potential of natural regeneration (Thomas and Agee, 1986). Forest fire and clear-cutting can directly influence plant diversity and sustainability of forest production through soil or forest floor distur- bance, altered habitat structure, removal of nutrients, or altered micro-climate condition in boreal forest ecosys- tem (Reich

^{et al}

., 2001). Thus, it is very important to

understand ecological changes in understory vegetation and soil properties after forest disturbance to investigate forest degradation as ecological indicators in Mongolia.

The objectives of this study were: 1) to investigate eco- logical changes in understory vegetation and soil prop- erties after forest fire and clear-cutting in Siberian larch stand, and 2) to discuss ecological indicators of forest degradation in Mongolia.

Materials and Methods

1. Selection of the study sites

The field study was conducted at the southern area of Khenti in Mongolia (Figure 1). This area lies between the southern fringe of the Siberian boreal forest and mid- Asia steppe zone, and it is about 80 km from the north- east of Ulaanbaatar. It is very sensitive and vulnerable to external disturbances due to its geographical character- istics and also had been continuously disturbed by peo- ple in the vicinity of Ulaanbaatar, capital of Mongolia.

The most dominant species is

Larix sibirica

, which is distributed between 1,500 m and 1,700 m, and it only exist in the northern aspect due to harsh climate condi- tion (average annual temperature ranges from -1.9 to -3.8

^o

C and annual precipitation ranges from 240 to 320 mm). Hardwood species such as

Betula platyphylla

,

Salix

spp. and

^Populus

spp. were invaded and occupied rapidly after forest fire and clear-cutting as pioneer spe- cies in this area.

Burned and clear-cut

L. sibirica

stands (having more than one ha disturbed), and reference

L. sibirica

stand as a control (which is undisturbed and adjacently located

Figure 1. Location of the study sites.

with each other) were chosen in this study (Table 1). It is estimated that forest fire and clear-cutting in this area occurred in the similar period, between 1965 and 1966, according to local record (written in Mongolian) and interview with the local people. In each study site, three 30 m

^×

30 m square plots, a total of nine plots were ran- domly established to investigate stand characteristics including overstory coverage and density of

L. sibirica

seedlings (Table 1), and to set subplots for understory survey and soil sampling.

2. Identification of understory vegetation

A total of 15 square subplots (2 m

^×

2 m) in each study site were set to investigate the composition of understory vegetation. Identification of understory species according to nomenclature of Grubov (1982) was conducted jointly with researchers from the Institute of Botany, Mongolian Academy of Sciences. The importance value, species diversity (richness, evenness, Shannon’s index and Sim- pson’s index) and similarity of all identified vegetation were calculated using the following formula (Ludwig and Reynolds, 1988; Kent and Coker, 1994).

3. Micro-climate data collection

Portable HOBO data loggers were launched in each stand with three replications to measure air temperature and relative humidity during the research period. All data were automatically collected with one-hour interval

and the daily mean temperature and relative humidity were calculated (BoxCar Pro 4.0, Onset Computer Cor- poration, USA).

4. Soil sampling and statistical analysis

In each study stand, soil samples were collected using soil auger at three soil depths: the forest floor (O) and mineral horizons (A and B) with five replica- tions. The soil samples were air-dried after collection and transported to Korea for analysis with consent from the Ministry of Nature and Environment of Mon- golia and the National Plant Quarantine Service in Korea. The physical and chemical properties of all soil samples were analyzed, such as moisture content, pH, soil texture, organic matter, nitrogen and phosphorous (Bigham, 1986; Klute, 1986). The differences in soil properties among the study plots were determined by analysis of variance (ANOVA) and Tukey’s Studen- tized Range test (SAS 8.2). The significance for all analyses was determined at

^α

=0.05.

Results and Discussion

1. Changes in understory vegetation after forest fire and clear-cutting

Composition of understory vegetation in

Larix sibirica

stands in Mongolia drastically changed after forest fire and clear-cutting (Table 2).

Table 1. Characteristics of the study sites.

Study sites Location Elevation

(m) Dominant species

in overstory Age

(yr.) Overstory

coverage Seedling density of

L. sibirica

(no./ha) Reference stand 48°03´N, 107°88´E 1,601

Larix sibirica

40-120 70% 1,520 Burned stand 48°03´N, 107°88´E 1,564

L. sibirica,Betula platyphylla

20-40 40% 320

Clear-cut stand 48°03´N, 107°88´E 1,550

B. platyphylla

10-30 10% 80

where

^IV

is the importance value,

^RF

is the relative frequency and

^RC

is the relative coverage.

where

R

is the species richness,

S

is the number of species observed in the sample and

n

is the total number of plots sampled.

where

E

is the species evenness,

H'

is the number derived from the Shannon diversity index and

H'

max is the maximum value of

H'

.

where

H’

is the Shannon’s index of diversity,

s

is the number of species observed in the sample,

ni

is the number of individuals belonging to the

ⁱ

th of s species in the sample, and

ⁿ

is the total num- ber of individuals in the sample.

where

^D

is the Simpson’s index of diversity,

^s

is the number of species observed in the sample,

ⁿi

is the number of individuals belonging to the

i

th of s species in the sample, and

n

is the total num- ber of individuals in the sample.

where

Ss

is the Sørensen’s coefficient of similarity,

x

is the number of species at site

A

,

y

is the num- ber of species at site

B

, and

z

is the number of common species at both sites.

IV %( ) FR RC %+ ( ) ---2

= R S 1– ln n( ) ---

=

E H′

H′max ---

=

H′ n_i

----n

⎝ ⎠⎛ ⎞ln n_i ----n

⎝ ⎠⎛ ⎞

i=1

∑

s

=

D n_i(n_i–1) n n 1( – ) ---

i=1

∑

s

=

Ss 2z

x y+ --- 100×

=

Table 2. Changes in Importance value (IV) of understory vegetation at reference, burned and clear-cut stands.

No. Species Reference stand Burned stand Clear-cut stand RF(%) RC(%) IV(%) RF(%) RC(%) IV(%) RF(%) RC(%) IV(%)

1 Vaccinium vitis-idaea 3.2 17.2 10.2

2 Carex amgunensis 4.0 13.6 8.8 4.0 9.2 6.5 4.0 5.6 4.8

3 Bromus inermis 2.9 7.8 5.3 3.8 9.5 6.6 2.6 1.7 2.1

4 Calamagrostis obtusata 3.2 6.6 4.9 1.9 2.1 2.0

5 Fragaria orientalis 3.5 4.6 4.0 3.2 7.9 5.5 3.4 4.5 4.0

6 Linnea borealis 2.9 4.8 3.9

7 Elymus sibiricus 3.7 3.0 3.4 0.8 0.3 0.6 4.3 3.2 3.8

8 Equisetum pratense 3.2 2.7 3.0 1.1 0.5 0.8

9 Vicia baicalensis 3.2 2.9 3.0 0.3 0.1 0.2

10 Aegopodium alpestre 4.0 1.6 2.8 3.0 1.5 2.2

11 Poa sibirica 3.6 1.9 2.7 1.6 0.9 1.3 2.3 1.8 2.0

12 Artemisia sericea 2.0 3.1 2.6 1.9 4.0 3.0 2.9 2.3 2.6

13 Galium boreale 3.2 1.8 2.5 2.2 2.4 2.3 2.9 1.2 2.1

14 Geranium pseudosibiricum 2.9 2.1 2.5 1.6 0.7 1.1 2.6 1.3 2.0

15 Festuca ovina 2.3 2.5 2.4 4.0 10.3 7.2 3.7 16.1 9.9

16 Lathyrus humilis 2.6 2.1 2.4 1.6 1.3 1.5 2.0 1.1 1.5

17 Artemisia tanacetifolia 2.6 2.1 2.3 3.5 3.3 3.4 2.9 3.6 3.3

18 Vicia cracca 2.6 1.9 2.2 3.8 2.6 3.2 2.9 2.2 2.5

19 Campanula Truczaninovii 2.9 1.1 2.0 2.7 1.6 2.1

20 Chrysanthemum zawadskii 2.9 1.1 2.0 3.5 1.4 2.4 3.7 2.4 3.1

21 Valeriana officinalis 2.6 1.3 2.0 1.9 0.7 1.3 2.0 1.0 1.5

22 Anemone crinita 2.6 1.1 1.8 1.1 0.5 0.8 2.6 1.8 2.2

23 Potentilla strigosa 2.3 1.1 1.7 2.7 1.8 2.3 1.1 0.3 0.7

24 Galium verum 2.0 1.1 1.6 2.2 1.4 1.8 2.0 1.4 1.7

25 Achillea asiatica 2.3 0.7 1.5 0.8 0.2 0.5 1.1 0.5 0.8

26 Carex lanceolata 1.7 1.0 1.4 3.5 5.3 4.4 0.6 0.1 0.3

27 Rubus arcticus 2.0 0.9 1.4

28 Aconitum barbatum 2.0 0.5 1.3 1.6 0.8 1.2 2.0 0.8 1.4

29 Pulsatilla flavescens 1.7 0.9 1.3 2.7 1.8 2.3 3.2 6.0 4.6

30 Artemisia integrifolia 1.4 0.6 1.0 3.2 2.8 3.0

31 Hedysarum hedysaroides 1.2 0.8 1.0 0.5 0.2 0.4 1.1 0.4 0.8

32 Polygonum alopecuroides 1.4 0.7 1.0 0.3 0.1 0.2 2.6 2.2 2.4

33 Sanguisorba officinalis 1.3 0.6 1.0 3.2 2.0 2.6 2.0 0.8 1.4

34 Trientalis europaea 1.4 0.5 1.0

35 Myosotis sylvatica 1.4 0.4 0.9 3.5 1.6 2.5 3.4 1.2 2.3

36 Ranunculus japonicus 1.4 0.3 0.9 1.3 0.5 0.9 0.3 0.1 0.2

37 Trollius asiaticus 1.2 0.7 0.9 0.8 0.3 0.6

38 Thalictrum minus 1.2 0.4 0.8 0.5 0.3 0.4 1.1 0.3 0.7

39 Cimicifuga foetida 1.2 0.2 0.7

40 Polemonium racemosum 0.9 0.2 0.6 1.1 0.7 0.9 2.6 1.5 2.0

41 Scorzonera radiata 0.9 0.3 0.6 1.9 0.8 1.4

42 Silene sibirica 0.9 0.2 0.6 0.5 0.2 0.4 2.6 1.0 1.8

43 Viola biflora 0.9 0.2 0.5 2.1 1.5 1.8

44 Dianthus superbus 0.6 0.2 0.4

45 Vicia venosa 0.6 0.3 0.4 0.8 0.2 0.5

46 Maianthemum bifolium 0.6 0.1 0.3

47 Pyrola incarnata 0.6 0.1 0.3

48 Polygonum viviparum 0.3 0.1 0.2 0.3 0.2 0.2

49 Aconitum czekanovskii 0.3 0.2 0.2

50 Agrostis mongolica 3.4 9.7 6.6

Vaccinium vitis-idaea

,

Carex amgunensis

and

Bromus inermis

were most abundant understory species in the reference stand. However,

Festuca ovina

and

Chamaen- erion angustifolium

were the dominant species in burned and clear-cut stands.

Chamaenerion angustifolium

(fireweed) was reported in the previous studies (Li

et al

., 2005;

Pugachev

et al

., 2005) as very well-known good post- fire indicator in Khenti area, Mongolia and Russian Far East. The species abundance and biodiversity indices were higher in the burned and clear-cut stands than ref- erence stand (Table 3). It was the result of increased for-

est gap due to elimination of upper layer trees by forest fire and clear-cutting. This provided better light environ- ment for the invasion and development of understory vegetation (Messier

et al

., 1998; de Römer

et al

., 2007).

There was positive result after forest disturbance on quantitative changes in species diversity but species compo- sition changed negatively, such as the boreal understory species was replaced by sedge and steppe species.

Vac- cinium vitis-idaea

,

Pyrola incarnata

,

Linnea borealis

and

Maianthemum bifolium

are boreal understory species which are distributed in humid and closed forest at high

Table 2. Continued.

No. Species Reference stand Burned stand Clear-cut stand

RF(%) RC(%) IV(%) RF(%) RC(%) IV(%) RF(%) RC(%) IV(%)

51

Allium senescens

0.3 0.1 0.2

52

Androsace septentrionalis

0.5 0.2 0.4

53

Artemisia lacianata

1.1 0.7 0.9

54

Aster alpinus

0.5 0.3 0.4

55

Bromus pumpelliana

2.3 1.7 2.0

56

Carex caespitosa

2.9 1.5 2.2

57

Carex duriuscula

1.9 0.7 1.3

58

Carex pediformis

1.7 1.1 1.4

59

Cerastium ceratoides

0.3 0.1 0.2 0.9 0.5 0.7

60

Chamaenerion angustifolium

4.0 8.4 6.2 3.2 7.3 5.2

61

Draba nemosa

0.3 0.1 0.2

62

Dracocephalum grandiflorum

1.3 2.8 2.1

63

Halenia corniculata

0.6 0.1 0.3

64

Helictotrichon schellianum

1.6 0.7 1.1

65

Moerhingia laterifolia

0.5 0.1 0.3

66

Pedicularis resupinata

0.3 0.2 0.2

67

Poa attenuata

0.9 3.1 2.0

68

Poa pratensis

0.3 0.1 0.2

69

Potentilla nivea

3.0 1.0 2.0 3.4 1.9 2.7

70

Primula farinosa

0.3 0.1 0.2

71

Rodiola rosea

0.5 0.3 0.4

72

Sedum aizoon

1.3 0.5 0.9

73

Stellaria graminea

0.3 0.1 0.2 2.0 1.0 1.5

74

Taraxacum officinale

2.3 1.2 1.8

75

Trifolium lupinaster

1.3 0.6 0.9 0.7 0.3 0.5

76

Trisetum sibiricum

1.3 0.7 1.0

77

Vicia amoena

2.7 2.3 2.5 0.3 0.4 0.3

Sum 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

*The blank indicates no species exist.

Table 3. Species diversity indices of reference, burned and clear-cut stands.

Diversity indices Reference stand Burned stand Clear-cut stand

Richness (

R

) 22.9 (3.7) 24.9 (2.9) 23.2 (4.4)

Evenness (

E

) 0.824 (0.064) 0.865 (0.038) 0.842 (0.034)

Shannon (

H’

) 2.577 (0.291) 2.779 (0.203) 2.635 (0.224)

Simpson (

D

) 0.8795 (0.0423) 0.9072 (0.0267) 0.8874 (0.026)

*Values in parenthesis indicate standard deviation.

altitude with strong shade-tolerance under dense conifers but they are very vulnerable to anthropogenic distur- bances, such as forest fire and clear-cutting in Mongolia (Zoyo, 2000).

In this study, they completely disappeared after forest fire and clear-cutting whereas sedge and steppe species, such as

Carex duriuscula, C. lanceolata, C. pediformis, Poa attenuata

and

P. pratensis,

newly invaded the area or increased their abundance. This result implied signif- icantly that forest degradation has seriously progressed in

Larix sibirica

stand in Mongolia after forest fire and clear-cutting due to loss of habitat and decline of species diversity on boreal understory vegetation. Moreover, intense occupation of tall sedge grass after forest fire and clear- cutting has a vital role as obstacle on natural regenera- tion of

Larix sibirica

, which possibly accelerated forest degradation process. Thus, boreal understory vegetation has important ecological implication, which can serve as an indicator of forest degradation as well as useful in monitoring restoration process in Mongolia.

The Sørensen similarity index of understory vegetation among the reference, burned and clear-cut stands was determined. The similarity coefficient of species compo- sition between reference and burned stands (73.6%) was higher than between reference and clear-cut stands (63.8%). This result indicates that clear-cutting activity changed species composition more differently compared to forest fire, which is supported by other studies (Ever- ett

etal

., 1990; Rees and Juday, 2002). Therefore, clear- cutting activities have more adverse effects on species composition and diversity of understory vegetation than forest fire in Mongolia.

2. Changes in microclimatic variables after forest fire or clear-cutting

Forest fire and clear-cutting activities sharply alter microclimatic conditions and mainly affect species com- position and stand development (Reich

et al

., 2001).

Microclimate variables, such as temperature and relative humidity (RH), in study plots were measured.

During the research period, temperature increased by an average of 1.6°C in burned stand and 1.7°C in clear- cut stand compared to reference stand, but RH sharply decreased up to 15.7% in clear-cut stand (Figure 2). This Figure 2. Daily mean temperature and RH in the study plots.

Table 4. Changes in physical soil properties after forest fire or clear-cutting.

horizon Soil Study sites Soil texture Water content

(%) Bulk density (g cm

⁻³

) Sand (%) Silt (%) Clay (%) Texture

O Reference 29.6 (2.7) 49.2 (2.3) 21.2 (0.5) loam 14.3 (2.2)

^a

0.9 (0.1) Burned 27.5 (2.8) 46.9 (3.2) 25.6 (5.5) loam

09.2 (1.2)^b

0.9 (0.2) Clear-cut 38.1 (4.2) 44.0 (4.5) 17.9 (0.9) loam

06.5 (1.0)^c

1.1 (0.1) A Reference 27.9 (1.4) 43.2 (3.2) 28.9 (2.9) clay loam 13.1 (3.5)

^a

1.2 (0.1) Burned 20.2 (4.0) 47.3 (6.6) 32.5 (3.3) clay loam

08.2 (0.6)^b

1.4 (0.1) Clear-cut 18.0 (2.5) 53.9 (0.6) 28.1 (3.1) clay loam

05.9 (1.0)^c

1.6 (0.1) B Reference 24.2 (5.7) 48.0 (11.7) 27.8 (7.2) loam

05.8 (0.8)^a

1.7 (0.1) Burned 18.9 (4.9) 49.5 (6.3) 31.6 (2.4) clay loam

04.9 (0.4)^b

1.6 (0.0) Clear-cut 26.5 (1.6) 48.5 (5.7) 25.0 (5.1) loam

03.9 (0.3)^c

1.7 (0.0)

*Values in parenthesis indicate standard error. Different letter indicate significant difference at

p

<0.05

result indicates that microclimatic condition of

Larix sibirica

stand became warmer and drier after forest fire and clear-cutting, and affected the species composition of understory vegetation. For instance, more sedge and grass species became abundant in burned and clear-cut stands compared to reference stand.

3. Changes in soil properties after forest fire or clear- cutting

Soil moisture significantly decreased after forest fire or clear-cutting, and the extent of decrease was more severe in the clear-cut stand (Table 4). This result indi- cate that changes in physical soil properties, such as water content and bulk density, were more negatively affected by clear-cutting activity than by forest fire. The loss of soil moisture resulted in the compaction of soil which accelerated soil erosion and harmfully affected to plant root growth (Gombosuren, 1992).

The chemical properties at soil organic layer were sig- nificantly affected by forest fire and clear-cutting but not the mineral horizons (Table 5). Forest fire stimulated the increase of pH while organic matter (OM) content sig- nificantly decreased. This was caused by ash deposition on surface soil and nutrient losses through leaching (DeBano

et al

., 1998; Fisher and Binkley, 2000). Clear- cutting activities stimulated the decrease of inorganic N (NH

4+

-N, NO

3−

-N). Inorganic nitrogen of the forest floor (O horizon) significantly decreased in the clear-cut stand compared to the burned and reference stands. Decreased nutrient and water uptake by vegetation, increased amounts of dead organic matter and changed soil hydraulic prop- erties all promote N leaching after clear cutting but degree of leaching depends largely on the types of oper- ation and its intensity (Piirainen

et al

., 2007). Available P of soil significantly increased after fire, whereas it decreased after clear-cutting. Therefore, the results indi- cate that clear-cutting activity rather than forest fire changed the soil properties more negatively. Loss of for-

est floor and surface mineral soil by improper clear-cut- ting activity can be a serious obstacle to the restoration or rehabilitation (Giardina and Rhoades, 2001).

4. Ecological indicators

Numerous studies have been attempted to develop eco- logical indicators for understanding ecological changes after forest disturbance and to monitor the ecological restora- tion process (Keddy and Drummond, 1996; Harris, 2003; Dodson

et al

., 2007; Nichols and Grant, 2007) at diverse forest ecosystems. SERI has produced a “Primer on Ecological Restoration (2004)” with nine ecological attributes, but some of them are conceptual and not real- istic. Ruiz-Jaen and Aide (2005) simply categorized the use of three attributes, such as vegetation structure, biodiversity and ecological processes, to achieve realistic goals. The development of ecological indicators is needed to understand ecological changes brought by for- est disturbance, to decide restoration techniques, and to monitor and value its achievement.

In this study, forest degradation process was identified by the composition of understory vegetation and forest soil properties in the

Larix sibirica

stand of Mongolia.

The existence of boreal understory species, such as

Vac- cinium vitis-idaea

,

Pyrola incarnata

,

Linnea borealis

and

Maianthemum bifolium,

was a very important indi- cator to define forest degradation in boreal forest, Mon- golia, whereas soil moisture and available P among soil physical and chemical properties were distinct indicators to detect changes in forest soil after forest fire or clear- cutting. It is expected that the result of this study can be applied to decide on restoration treatments and to prac- tically monitor restoration process in the

Larix sibirica

stand of Mongolia.

Conclusions

Forest fire and clear-cutting activity significantly affected

Table 5. Changes in pH, OM and nitrogen contents of forest soil after fire or clear-cutting.

horizon Soil Study sites pH OM

(%) TN

(%) Inorganic-N

(mg kg

⁻¹

) TP

(mg kg

^-1

) Available-P (mg kg

⁻¹

) O Reference 5.4 (0.3)

^b

13.2 (0.9)

^a

0.71 (0.04) 5.0 (2.3)

^a

450.5

08.1 (1.3)^b

Burned 5.8 (0.2)

^a 09.3 (0.6)^b

0.69 (0.16) 4.5 (2.3)

^a

532.4 37.5 (2.7)

^a

Clear-cut 5.4 (0.2)

^b

12.0 (0.5)

^a

0.74 (0.11) 1.1 (0.4)

^b

413.7

02.3 (0.5)^c

A Reference 5.4 (0.5)

^b 07.5 (0.9)

0.25 (0.08) 2.0 (0.6) 181.5

02.9 (1.5)^b

Burned 6.2 (0.1)

^a 06.1 (0.5)

0.23 (0.06) 0.9 (1.3) 307.7

04.5 (1.6)^a

Clear-cut 5.6 (0.2)

^b 07.1 (0.2)

0.22 (0.03) 0.2 (0.0) 301.0

01.4 (0.2)^c

B Reference 6.0 (0.2)

04.6 (0.7)

0.09 (0.08) 0.2 (0.2) 137.9

01.3 (0.5)^b

Burned 6.4 (0.4)

03.7 (1.0)

0.08 (0.02) 0.1 (0.1) 176.8

02.2 (1.4)^a

Clear-cut 6.1 (0.4)

04.3 (0.5)

0.04 (0.01) 0.0 (0.0)

091.7 01.2 (0.1)^b

*Values in parenthesis indicate standard error. Different letters indicate significant difference at

p

<0.05

understory vegetation and soil properties in the

^Larix

sibirica

stands of Mongolia. The boreal understory spe- cies replaced into sedge and steppe species after forest disturbance and the similarity coefficient of species com- position between reference and burned stands was higher than between reference and clear-cut stands. The phys- ical and chemical soil properties were significantly changed after forest disturbance, and it was more neg- atively in the clear-cut stand. Therefore, clear-cutting activity affected more negatively the understory compo- sition and soil properties compared to forest fire. The existence of boreal understory species was an important indicator to define forest degradation in boreal forest of Mongolia while soil moisture and available P among soil physical and chemical properties were distinct indicators to detect changes in forest soil after forest fire and clear- cutting. Therefore, the results of this study could be use- ful in identifying ecological indicators of forest degra- dation, making decision on restoration treatments and monitoring restoration process in Mongolia.

Acknowledgement

This study was supported by the Korea Research Foundation (KRF-2006-214-F00009).

Literature Cited

1. Angelstam, P.K. 1998. Maintaining and restoring biodi- versity in European boreal forests by developing natu- ral disturbance regimes. Journal of Vegetation Science 9(4): 593-602.

2. Bigham, J.M. 1986. Methods of soil analysis, Part 3, Chemical methods. 2nd edition. Monograph No. 9, ASA, Madison, Wisconsin.

3. Clewell, A. F. and J. Aronson. 2006. Motivations for the restoration of ecosystems. Conservation Biology 20(20): 420-428.

4. DeBano, L.F., D.G. Neary and P.F. Ffolliott. 1998.

Fire’s Effects on Ecosystems. John Wiley & Sons, Inc.

333pp.

5. de Römer, H. André, D.D. Kneeshaw and Y. Bergeron.

2007. Small gap dynamics in the southern boreal forest of eastern Canada: Do canopy gaps influence stand development? Journal of Vegetation Science 18: 815- 6. Dodson, E.K., K.L. Metlen and C.E. Fiedler. 2007. 826.

Common and uncommon understory species differen- tially respond to restoration treatments in ponderosa pine/douglas-fir forests, Montana. Restoration Ecology 15(4): 696-708.

7. Everett, R., D. Zabowski and P. McColley. 1990. Veg- etative restoration of western-montane forest soils.

Pages 29-31 in Proceedings of Management and Pro- ductivity of Western Montane Forest Soils. April 10- 12, 1990. Boise, ID, USA.

8. Fisher, R.F. and D. Binkley. 2000. Ecology and Man- agement of Forest Soils. John Wiley & Sons. USA.

489pp.

9. Giardina, C.P. and C.C. Rhoades. 2001. Clear cutting and burning affect nitrogen supply, phosphorus frac- tions and seedling growth in soils from a Wyoming lodgepole pine forest. Forest Ecology and Management 140: 19-28.

10. Gombosuren, N. 1992. The Role of Sub-taiga Larch Forest for Water Regulation and Soil Conservation at Eastern Khenti, Mongolia. Ph. D. Dissertation. Agri- cultural University. Ulaanbaatar, Mongolia.

11. Grubov, V.I. 1982. Key to the Vascular Plants of Mon- golia. Science Publisher Inc. USA. 817pp.

12. Harris, J.A. 2003. Measurements of the soil microbial community for estimating the success of restoration.

European Journal of Soil Science 54: 801-808.

13. Keddy, P.A. and C.G. Drummond. 1996. Ecological properties for the evaluation, management, and resto- ration of temperate deciduous forest ecosystems. Eco- logical Applications 6(3): 748-762.

14. Kent, M. and P. Coker. 1994. Vegetation Description and Analysis: A Practical Approach. John Wiley &

Sons. 363pp.

15. Klute, A. 1986. Methods of soil analysis, Part 1, Phys- ical and Mineralogical Methods. 2nd edition. Mono- graph No. 9, ASA, Madison, Wisconsin.

16. Krzic, M., R.F. Newman and K. Broersma. 2003. Plant species diversity and soil quality in harvested and grazed boreal aspen stands of northeastern British Columbia. Forest Ecology and Management 182: 315- 17. Li, S.-G., J. Asanuma, A. Kotani, W. Eugster, G. Davaa, D. 325.

Oyunbaatar, and M. Sugita. 2005. Year-round measure- ments of net ecosystem CO

2

flux over a montane larch forest in Mongolia. Journal of Geophysical Research 110: D09303, doi:10.1029/2004JD005453.

18. Ludwig, J.A. and J.F. Reynolds. 1988. Statistical Ecol- ogy. Wiley Interscience, New York. 337pp.

19. McLachlan, S.M. and D.R. Bazely. 2001. Recovery patterns of understory herbs and their use as indicators of deciduous forest regeneration. Conservation Biology 15: 98-110.

20. Messier, C., S. Parent and Y. Bergeron. 1998. Effects of overstory and understory vegetation on the under- story light environment in mixed boreal forests. Journal of Vegetation Science 9(4): 511-520.

21. Ministry of Nature and Environment of Mongolia. 2002.

State of the Environment of Mongolia. Ulaanbaatar.

57pp.

22. Nichols, O.G. and C.D. Grant. 2007. Vertebrate fauna

recolonization of restored Bauxite mines - Key findings from almost 30 years of monitoring and research. Res- toration Ecology 15(4): 116-126.

23. Ohlson, M., L. Söderström, G. Hörnberg, O. Zackrisson and J. Hermansson. 1997. Habitat qualities versus long- term continuity as determinants of biodiversity in Boreal old-growth swamp forests. Biological Conser- vation 81: 221-231.

24. Piirainen, S., L. Finér, H. Mannerkoski and M. Starr.

2007. Carbon, nitrogen and phosphorus leaching after site preparation at a boreal forest clear-cut area. Forest Ecology and Management 243: 10-18.

25. Pugachev, A.A., E.A. Tikhmenev and P.E. Tikhmenev.

2005. Natural recovery of technogenic landscapes in open larch forests in northeastern Russia. Russian Jour- nal of Ecology 36(6): 391-395.

26. Rees, D.C. and G.P. Juday. 2002. Plant species diver- sity on clear-cut versus burned sites in central Alaska.

Forest Ecology and Management 155: 291-302.

27. Reich, P.B., P. Bakken, D. Carlson, L.E. Frelich, S.K.

Friedman and D. F. Grigal. 2001. Influence of logging, fire, and forest type on biodiversity and productivity in southern boreal forests. Ecology 82(10): 2731-2748.

28. Ruiz-Jaen, M.C. and T.M. Aide. 2005. Restoration suc- cess: How is it being measured? Restoration Ecology 13(3): 569-577.

29. Society for Ecological Restoration International Sci-

ence & Policy Working Group. 2004. The SER Inter- national Primer on Ecological Restoration. www.ser.org &

Tucson: Society for Ecological Restoration Interna- tional.

30. Thomas, T.L. and J.K. Agee. 1986. Prescribed fire effects on mixed conifer forest structure at Crater Lake, Ore- gon. Canadian Journal of Forest Research 16: 1082- 1087.

31. Tsogtbaatar, J. 2004. Deforestation and reforestation needs in Mongolia. Forest Ecology and Management 201(1): 57-63.

32. United Nations Environment Programme (UNEP). 2002.

Mongolia: State of the Environment. Ulaanbaatar.

33. Venturelli, R.C. and A. Galli. 2006. Integrated indica- tors in environmental planning: Methodological consid- erations and applications. Ecological Indicators 6: 228- 34. Wyant, J.G., R.A. Meganck and S.H. Ham. 1995. A 237.

planning and decision-making framework for ecologi- cal restoration. Environmental Management 6: 789- 35. Zoyo, D. 2000. The changes of herbaceous and bush 796.

cover in larch and pine forests after cutting and forest fire. Ph. D. Dissertation. Mongolian National Univer- sity, Ulaanbaatar, Mongolia.

(Received August 31, 2009; Accepted October 8, 2009)